Transmission system



April 12, 1932. J. L. HOGG ET AL TRANSMISSION SYSTEM Filed April 19, 1930 J. 'L. Hose By 5: 005A m) VE/V 70/95.

A TTOHNL') Patented Apr. 12, 1932 JOHN. n'fnoee; or nAsr-oRANGny-Nmv 'annsnvgnnn STEPHEN-"DOBAfOF- *BROQKLYN,

NEW YORK, Assremons TO'IBELL TELEPHONE? LABORATORIES; INCORPORATED; or

NEW YORK, 1\T.'Y., A CORPORATION.- or NEWYORK rRANsMIssIoN' -sYsrEM Application fil'eiir'npril '19,

on a condenser to maintain the volume of energy at a desired point on the system Within a predetermined range. Another ob'ect of the invention is to provide a signal transmission system withtrans mitt-ing and receiving channels eachhaving a vacuum tube lossdevice connectedthereto under the control'of a capacity element that shall efi ect a decreased loss in one channel when an increased loss is effective in the other channel and that shall control the charging and V dischar 'ing 0f the capacity element in an improved-manner. j

A further object ofthe invention is topro- 'vide a four-Wire transmission systemwith; a vacuum tubeloss device-connected in series with one channel and: a vacuum tube lossde vice connected across the other channel that shall have a capacity element-.1201 controlling thepotential onthei grids of the'loss devices to govern the energy volume onthe system in improved manner. r

Infsignal transmission systems there are many cases where it is verydesirable to-hold the voltage-s01" the signal or speech currents Within a predetermined range. Int-he trans- I atlantic radio system, itisnecessary to'hold the voltages on the system in. iirontot-the radio transmitter Within-alimit Whichivill "transmission 'stem within predetermined limits. The potential onthexgrids oi the vacuum tube 'l'oss devicesis. governed accord ingto the charge on: a 'condenserand the charge on the condenser is automatically .1930. Serial no, 44,5543.

controlled. in accordance with the loss desired in the systemi The finvention has been illustrated by .meanso'fa tour-Wire transmission: system having vacuum tube loss devices. in .thetrans- ,mittingand receiving channels. transmitting .chann'e l two ,three-element thermionic tubes are connected. in'push-pull "relationship I for controlling. the" impedance of such channel. The-anode-cathode-- circuits of such tubes are connected in series Withithe channel- .so that the potential onithe grids of the tubes may be. controlled to vary the impedance efiected-in the-chann'elby the tubes. The potential impressed on :the grids of the .tubes is controlled incaccordance =Wltl'l the peaks of speech current. beyond Lthe impedance means comprising the two-thermionic tubeszin push-pull relationship.

.in'g channel comprises two three-element thermionic tubes vinqoush oullrelationship in the I-he vacuumtu-be loss d'evice inthe-receiv-J having their anode cathode circuits con-nected across the receiving." channels A com: denser. is. providedffor controllingnot. only the-potential impressed on thegridsof-the impedance t ubes'in the transmitting channel, butalso the potential iimpressed ontt'h'e grids of the impedance-tubes in :the receiving .ch-an' .nel; The --charge-on the condenser-isfcontrolled in accordance with thepea'ks DIE-"the speech current beyond the impedance tubes in the transmitting channel. By connecting ..the impedance tubes in series with the transmitting channel andcacross ether-receiving channel, itv will be -n0ted.fthatany increased charge on said condenser will be accompanied bya corresponding decreased losspin the receiving channel.--I-t is necessary f'to channel in. an oppositeemannerto the [im- .losscaused in the transmitting'channel by'a V 'pedancemeans in the transmitting channelin order to .maintain the four-wirecircuit balanced and prevent any singing conditions.

. Means: are. providedfo'r' preventing charging of the 'condenseriuntil the-peaks of speech icurrent: beyond the impedancetubes :in thef .transmlttlng channel area above aniupper 11m.-

aroc iting value. fiWhen the zupper limiting value of the peaks of speech-in the transmitting channel beyond the impedance tubes is reached, the condenser which controls the impedance tubes in the transmitting and receiving channels is charged in accordance with the energy volume in the transmitting channel beyond the impedance tubes. Means are further provided for either discharging the V condenser or preventing furthercharging of it when the peaks of speech on the transmitting channel beyond the impedance tubes therein fall below a lower limiting value. If the peaks of speech current on the transmitting channel beyond the impedance tubes are below the lower limiting value and the peaks of speech of the transmitting channel before the impedance tubes are above the peaks of speech current for a weak talker, the condenser is discharged. If the peaks of speech current beyond the impedance tubes in the transmitting channel fall below the lower limiting value and the peaks of speech current on the transmitting channel before the impedance tubes fall below the peaks of current for a weak talker, then further charging of the condenser is prevented and the charge thereon is held for a limited period. Thus, when conversation ceases for a short period the setting of the impedance means on the line is held for a short period.

In some respects the volume control circuits operate similar to the circuits disclosed in the application of R. C. Mathes Serial No. 37 2,951, filed June 22, 1929, which became Patent 1,810,025, June 16, 1931. The control for the impedance means is obtained from the transmitting channel beyond the impedance meansand the energy level in the transmitting channel is held between an upper and a By holding the en.

mitting channel 3 and a receiving channel 4. The transmitting'channel comprises a three element thermionic amplifier tube 5, a vacuum tube loss device 6 and two'thermionic amplifier tubes 7 and 8. The vacuum tube loss device 6 comprises two three-element thermionic tubes 9 and 10 which are connected in push-pull relationship. A transformer 11 which is connected to the two wire circuit comprising conductors 1 and 2 is connected to the input circuit of the amplifier tube by means of a potentiometer 12.

The impedance tubes 9 and are connected to the amplifier tube 5 by means of a transformer 13 having a primary winding 14 in the output circuit of the amplifier tube 5 and two secondary windings 15 and 16. Resistance elements 17 and 18 are connected across the secondary windings 15 and 16 of the transformer 13. The resistance elements 17 and 18 have an impedance which is relatively low as compared with the impedance of the tubes 9 and 10. The output circuits of the impedance tubes 9 and 10 are connected by a transformer 19 to the input circuit of the amplifier'tube 7. A resistance element 20 having a low value as compared with the impedance of the tubes 9 and 10 and of the order of the sum of the impedances of the resistance 17 and 18 is connected across the primary of the transformer 19. The amplifier tube 7 is connected to the amplifier tube 8 by means of a transformer 21 and the output circuit of the amplifier 8 is connected to a transformer 22.

In the receiving channel 4 are inserted two transformers 23 and 24. The transformers 23 and 24: serve as step-up transformers. Between the transformer 24: and transformers 25 and 26 is inserted a vacuum tube loss device 27 comprising two three-element thermionic tubes 28 and 29. The two tubes 28 and 29 are connected in push-pull relation ship with their anode-cathode circuits across the receiving channel. The plates of the tubes 28 and 29 are directly connected to the channel conductors and the filaments of such tubes are connected to the channel conductors by means of an inductance 30. Between the primary winding of transformer 25 and the inductance 30 are inserted resistance elements 31 and 32 and between the secondary winding of transformer 24 in the impedance tubes 28 and 29 are inserted resistance elements 33 and 34. The impedance of the resistance elements 31 to 34, inclusive, is relatively high as C p d to the impedance of the thermionic tubes 28 and 29. The transformers 25 and 26 are step-down transformers and have a ratio of transformation similar to the ratio of transformation of the transformers 23 and 24:. The transformer 26 I connected to the transmitting channel and the 7 tubes 28 and 29 connected to the receiving channel. A negative potential impressed on the grids of the tubes 9 and 10 will increase the loss in the transmitting channel, whereas a negative potential impressed on the grids I";

of the tubes 28 and 29 will decrease the loss in the receiving channel. The condenser is charged from the output circuit of the amplifier tube 8 in the transmitting channel. by

a circuit comprising thermionic tubes 36, 37,

38 and 39. i The input circuit of theamplifier tube'39 islcon-nected to a: potentiometerAO in} the output circuit. of" the amplifier 'tube-i8.;. The output circuitoi the tube 39 is connected: tov the rectifier tube 38 by a transformer 41.1

The output circuit of the rectifier tube. '38. connected to the amplifier tube 37 bya potene tiometer 42. The outputcircuit of thevam-J pli'tier'v tube 37 isconn-ected to the amplifier 1"; tube 36 by a potentiometer 43 and'the output.

I circuitxof the amplifier tube 36 is directly con nected to the'condenser'35w V VVh'en the peaks of speech current in the output circuitfof theampli'fier tube v8 are below an upperlinntingnvalue, the grid of the rectifier tube 38 is maintained. strongly negative by means ofbattery 44; This insures substa'ntially zero potential between the grid and filament" of the" amplifier tube 37'. HoWeven-there is au sub'stantial current flow through. the amplifier" tube 37 and the. po-

' tentiometer'43. The'p'otential drop across a portion of the potentiometer .43 adds to the: A negative potential impressed on the-gridxof the amplifier tube 38. The connection of the potentiometer .43 to the grid Iofthe amplifier tube 38is efiected'bymeans of a conductor '45) The potential drop across the potentiometer 43 also maintains the: grid of the amplifier .1 tube 36 strongly negativeso that IlOhCLlII'QIliT,

flows in-the output circuit of the amplifier. tube 36 for chargingthe'condenser 35; 1 If the peaks of speech current'in-the output circuit of the amplifier: tube Suare: raised; above the upperlimitingvalue the negative potential on the grid ofthe"amplifier'tube 38 is reduced to impress potential on the "grid of the amplifiertube 38; It may be'noted that the potentiometer 42 is relatively large and a small current flowtherethrouglr-will. produce a substantial change in theoutput of the amplifier tube 37 andrthe current flow through-the potentiometer 43. Thus, alarge;

. and very abrupt change is efi'ected in the potential applied betweenthe grid and fil'ament,

of the amplifier tube 36. 1

The charging: current from the output. of

the'amplifier tube 36 for the condenser 35 will last only during the time that the energy 'in:

the output circuit of the amplifier tube SYis above the upper limiting value. f The'instantt such'voice Wave peaks fall below theupper limiting. value, the charginglofthe condenser 35 stops. The charge on the-condenser, how

everyv is retained and when. another'peak of the voice waves beyond the amplifier s rises; above the upper limiting value another-nine? erement of charge is impressed on the cone? denser 35. The chargeis retained on the cone denser 35 when the peaks otvoice waves-be yond' tliexamplifier 8 :fall below thez-upper 57' which blocks the tube 57-to insure eter 143 increases H to impress avhigh n'egativei potential on thel'gridiofthetube 36; The Vim-- pressing of a high: negativetpotential on; the 'gridloi the? amplifier .tube 36 causes :theim pedance in: the; ChaI-glIIgIiClICUlt 'Of tl11iCOI1-= densen 35 to beeraised to a very high: value; Theabove mentionedxcircuits can be adjusted sothat the-'rdischarge f theicondenser-35 is very" slow and little. change in: the charge Will'be' ol'iserved after ':a period of fivemin utes. m

The. discharge of the conde'nser' 35i is ef fectedby means of a control relay 48having. an armature 49 and aniauxiliary relayi 50- havingan armature 15 1. The relay'48 'is: con-' trolled from the'output of the amplifier' tubes -inthetransmitting channel 3 before the' V impedance tubes 9 and- The auxiliary 1 relay 50? is controlled bytthe' potentiometeri in the'output of I the amplifier tube 8 'in' thetransmittingchanneh In the' released position;;the armature 51 0f the' irelayz is' biased to engage the contact member 52;? VWhen' the relay 50 is operatedthe. armature 51 is moved intocngagement with the con tact member 53Q The farmature"49"0f the relay 48 is biaseclto engage thestop member '54 when the relay isgin released position-.1

The armature 49 is held in engagementwith the contact member 55 when the relay 348 is operated. c g I T i A potentiometer 56 intheioutput circuit' of" the amplifier tube 5 is'connected to the'input circuit of an amplifier tube 57; The output circuit of the amplifier tube 57 is connected by transformer "58 to the :input' circuit of an amplifier tube 59.? Theoutpu't cir'cuit-of V the amplifier; tube 59 is connectedby'a transa for-mer'GO to the input circuit'ofa detecton tube'61." The'output circuit of'the detector? tube 61 is connected to the "control relay 48.

When the peaks ofthe voice currents'in the output circuit-otthe amplifier tube'5 are above thepeak's of avery weak talker, the amplifier tubes57and 59 and'the detector tube 61 supply current for operating-the consistance element 63'connected across itis connected in the input circuit of the amplifier tube 57. The condenser 62 is charged from a batterv64 when'the auxiliary-relay lease of the control relay 48;

trol relay 48.- A condenser'62 having a re- Theauxiliary relay 5O is'operated from the potentiometer 4O int-the transmitting channel by means of an amplifier .tube 65;rand1ade tector tube 66; The auxiliarymelay. 50. is operated whenthepeaks OfHVOlCO current theoutput circuit of the zamplifier tube 8 are' above a lower limiting value; It the auxil iary relay SO is inreleased position-Whilethecontroli relafyr48-is in an operative position;

it will be noted condenser 35 is discharged through a resistance element 67.

Assuming the control relay 48 and the auxiliary relay 50 to be in the positions shown on the drawing and conversation to take place over the four-wire system, the relay 48 would be operated as soon as the peaks of the voice currents in the output circuit of the amplifier tube 5 rises above the peaks of voice current for a weak talker. It may be noted that the high negative potential impressed upon the grid of the rectifier tube 38 insures against any charging of the condenser 35 until the peaks of the voice currents in the output circuit of the amplifier tube 8 rise above the upper limiting value. When the peaks'of the voice currents in the output circuit of the amplifier tube 8 rise above the lower limiting value, the auxiliary relay 50 is operated. When the auxiliary relay 50 is operated, the condenser 62 associated with the amplifier tube 57 is charged to block the tube 57 and release the relay 48. I

The system will remain in this position it the peaks of the voicecurrents in the output circuit of the amplifier tube 8 remain between the upper and lowerlimiting values. If the" peaks of the voice currents in the output circuit of the amplifier tube 8.rise above the upper limiting value, the amplifier tubes 36,-

37, 38 and 39 impress a charge on the condenser 35. The charge on the condenser 35, as before set forth. impressesnegative poten tial on the grids ofthe two impedance tubes 9 and 10 inthe transmitting channel and the grids of two impedance tubes 28 and 29 in the receiving channel. The placing of negative potential on the grids 9 and 10 in the transmitting channel adds to the loss in the trans mitting channel whereas the negative potential impressed upon thegrids of the tubes 28 and 29 in the receiving channel reduces the loss in the receiving chanel.

Whenever the peaks of the voice frequency currents in the output circuit of the amplifier tube 8 fall below the upper limiting value, charging of the condenser 35 ceases. How ever, no substantial discharge of the I condenser 35 takes place immediately unless the peaks of the voice frequency currents in the output circuit of the amplifier 8 fall below the lower limiting value. If the peaks ot the voice frequency currents in the output circuits of the amplifier tube 5 in the transmitting channel are above the peaks of voice free quency currents for a weak talker to operate the control relay 4S and the peaks of speech in the output circuit of the amplifier tube 8 fall below the lower limiting value. then the auxiliary relay 50 is in released position when the control relay is in an operative position. The condenser 35 is then discharged through the resistance element 67 to decrease the impedance in the transmitting channel and increase the impedance in the receiving channel.

. If conversation ceases for a brief period of time, the charge on the condenser 62 impresses a strong negative potential on the grid of the amplifier tube 57 which controls the control relay 48. The slow discharge of this condenser 62 prevents any immediate operation of the control relay 48. This insures if conversation is immediately resumed that the setting of the volume control circuits will remain unchanged.

Modifications in the system and in the arrangement and location of parts may be made within the spirit and scope of the invention and such modifications are intended to be covered by the appended claims.

Vfhat is claimed is:

1. In a transmission system, transmitting and receiving channels, a vacuum tube loss device connected in series with one of said channels, another vacuum tube loss device connected across the other channel, and means to control the grid potentials of said devices in accordance with the volume of energy present at av point on one of said channels.

2. In a transmission system, transmitting and receiving channels, a vacuum tube loss device having its anode-cathode circuit connected in series with the transmitting channel, a vacuum tube loss device having its anode-cathode circuit connected across the receiving channel, and means. to control the grid potentials of said devices in accordance with the volume of energy present at a point on one of said channels.

3. In a transmitting system, transmitting and receiving channels, a vacuum tube loss device having its anode-cathode circuit connected in series with the transmitting channel, a vacuum tube loss device having its anode-cathode circuit connected across the receiving channel, a condenser for controlling the potential on the grids of said devices'and means for charging said condenser according to the energy volume on the transmitting channel beyond the device therein.

4. In a transmitting system,transmitting and receiving channels, a vacuum tube loss device having its anode-cathode circuit connected in series with the transmitting channel, a vacuum tube loss device having its anode-cathode circuit connected across the receiving channel, a condenser for controlling the potential on the grids ofsaid devices, and means for charging said condenser according to the energy volume on the transmitting channel beyond the device therein and for preventing charging of the condenser until the energy volume in the transmitting channel beyond the device .therein is above an upper limiting value.

5. In a transmitting system, transmitting and receiving channels, a vacuum tube loss device having its anode-cathode circuit connected in series with said transmitting channel, a vacuum tube loss device having its lie aaws anodegcathode circuit connectedacrosstherecei ving chan el, and means comprising a o l enl r for, varying? e 'pd e f l" Qii e; grids of said devices according to the energy. v

53volu1ne on one .of aiaje annei's eyo a'u e loss device therein to cause an increasedloss]; np e cha nel h ide rre p nd nai' d se I loss in the other'tlchannel or, vice versallirv respective fof theQ Ifr'e'quency. of the currents lq transmittedi I f In a transmissionf system, transmitting and. receiving channels a vacuum tube loss, devicehavingrits anode-cathode circuit connected infseriesiwithoneof said channels, a

5;? Vacuum tube loss 7 device I having its anode cathode] circuit connected across the other,

channel, means comprising' a'condenser for h I v I a a signal line, a vacuum tubelossdevice havf varyingthe potential onfthe grids of said de vices according to theen ergy volume on one, 950f said channels adjacent the as esses therein .to cause an increased loss in one channel and a corresponding decreased loss in the a other channel or vice versa irrespective of the frequency of the currents transmitted, and means for charging said condenser when the energy volume beyond the device in on e chane nel is above a'n upper limiting value and for" preventing charging of the condenser when the energy volume beyond the device in said ilast mentioned channeliis below the upper;

limiting value. I 7 A transmission system comprising a signal line,a vacuum tube lossfldevice connected 5 directly in series with said line, a condenser, means for varying the charge oni said condenser according to the volurne of energy present in said line adjacent to said device, and means for varying the potential on the grid of -said device according to the charge hon the condenser. I

8L In a transmitting control system, a signal line, a vacuum tube loss device connected directly in series with said line for controlling the energy volume transmitted over the iline, means comprising a condenser for varying said loss device according to the charge on the condenser, and means for charging said condenser according to the energy volume on the line beyond said loss device and 9for preventing charging of the condenser until the energy volume on the line beyond the loss device-is above an upper limiting value. a

9. A transmission controlsystem compris- ?ing a signal line, a vacuum tube loss device having the anode-cathode circuit thereof connected directly in series with said line, means comprising a condenser for varying the potential on the grid of said device in acicordance with the volume of energy present in said line beyond and adjacent to said de-' vice, and means for preventing charging of said condenser until a predetermined energy volume is present in said line and for insuring g'the discharging of; said condenser when the thereof connected directly in series with energy volume/on" the line beyond T 7% thefdeviceand means (comprising two-rela s respectively controlled by the volume-"of eIi-f ergy in the'linefon opposite s'idesfof'said de J vice 'for governing the discharging of said condenserwhenthe device inserts'la greater T Q loss in the linethan isdesiredf. w 11. In. a transmission system comprising ing. the,fanfode{cathode circuit thereof con} nected in serieswithfthe line for effecting aeg variable loss on the line, means, comprising condenser for varying the potential n the gridio'f said lossdevice tol control the loss caused thereby, means for charging the eon-j denser when the, energy volume onfftli me: beyond the device is above 'anupp'erlimiting; nd? e n for pr ven nst ise a eel of the coiidenser until the energy volume be p yond thegdevice' is belowjan'dtherandlowe j limiting value. f 12. In a transmission system c omprising a signalline', a three elementvacuuin tube oss? device having the anode-cathode circuiti line,means coinprisingla condenserqforvary ing the potential onthe grid of said les ee; viceto cdntrol" the los s ,(3ai1is6Q byithe d vice means for 'chargingthfe condenserwlienlth volume ofenergy on the linebeyonclj theid s 7 Vice is above, an "upper, limiting I value to in; my 1% crease th ,i 1o s caus ,je;1' bythejdeyicg and; m ans, iorfpr nangdi charge t e c a denser. until the, volume of energy on lin j beyond the device i b low. a lower-limiting value and 'thejpeaks of signal current be ore"; 119 ii e v a areabpy' hl' new; v ry, weakitalker. 13. Ina t'ransmission syst compri a signal line; a three-element acuiim Y o sg evi icom ect din slfi swiths 1 1 means comprising a condenser forgovarying the potential on thefgrid ofsaid 'lo 'ss e f to control the loss caused thereby, means for erei g' t l' llde erl wh t fv h r i 1 t.

ne gy on he l neibeybnd t d vi e,isfabovl 7 Value 14. In a volume control system, a signal line, a vacuum tube loss device in series with said line, a condenser for varying the potential on the grid of said device to control the loss caused by the device, means for charging said condenser in accordance with the energy volume on the line beyond the device when the volume of energy beyond the device is above an upper limiting value, a control relay, means for operating said control relay when the volume of energy on the line before the device rises above a minimum value, an auxiliary relay, means for operating said auxiliary relay when the volume of energy on the line beyond the device is above the lower limiting value, means for releasing the control relay when the auxiliary relay is operated, and means for discharging said condenser when the control relay is in opertherein when the volume of energy beyond the device in the transmitting channel is above an upper limiting value, a control relay, means for operating said control relay when the volume of energy on the transmitting channel before the device therein rises 40- above a minimum value, an auxiliary relay, means for operating said auxiliary relay when the volume of energy on the transmitting channel beyond the device therein is above the lower limiting value, means for re- 45 leasing the control relay when the auxiliary relay is operated, and means for discharging said condenser when the control relay is in operative position and the auxiliary relay is in released position.

16. In a transmission system, a signal line, a vacuum tube loss device connected to said line for varying the loss therein, means comprising a condenser for varying the potential on the grid of said device, means for varying the charge on said condenser in accordance with the energy volume on the line beyond said device and means for preventing variation of the charge on the condenser whenthe peaks of signal current before the loss device are below a predetermined level.

17. In a transmission system, a signal line, variable impedance means connected to said line for controlling the energy volume transmitted over the line, means comprising a condenser for varying said impedance means according to the'volume of energy present at a point in said system and means for preventing variation of the charge on the eondenser when the peaks of signal current before the loss device are below a predetermined level.

18. In a transmission system, a signal line, a vacuum tube loss device connected to said line for controlling the energy volume trans- .mitted over the line, means comprising a condenser for varying the potential on the grid of said device according to the volume of energy present at a point in said system and means for preventing variation of said loss deviceto change the charge on the condenser when the volume before the loss device is below a predetermined level.

19. In a transmission system, a signal line, a loss device connected to said line, means for controlling the loss device according to the energy volume on the line beyond the loss device, and means for preventing control of said loss deviceby the first mentioned means when the peaks of the energy volume on the line before the loss device are below a predetermined level.

20. A transmission line, a loss device connected to said line, means for controlling said loss device according to the energy volume on the line beyond the loss device, and means governed by the peaks of energy volume on said line before the loss device for preventing operation of said first mentioned means under predetermined energy volume conditions on the line before the loss device.

In witness whereof, we hereunto subscribe our names this 11th and 17th days of April,

JOHN L. HOGG. STEPHEN DOBA. 

